29 
which they attache1 themselves ; and the epiphytes, or those which 
simply grew on the bark or external covering of plants, and deriving 
no sustenance from them. 
In the same manner among animals, there were at least three kinds 
of companionships found, viz., the Efzzoa, which lived on and at the 
expense of their hosts ; the Etozoc, which took toll of the tissues of 
those animals within which they dwelt ; and two other companionships 
in which the animals did not seem to make their host pay any other 
toll beside that of affording them either a resting-place or shelter. 
One form of these lived on the outside of other animals, travelling 
as they travelled, being dependent on them much in the same way as 
railway passengers were who simply used the carriages as a means of 
getting from place to place, and did not derive any nutriment from the 
juices or tissues of the animals to which they attached themselves, any 
more than the barnacles did from drift-wood or a ship’s bottom. 
Another form of companionship was that in which, side by side 
and within the same dwelling, animals of a totally different order 
lived together, just as lodgers or boarders who occupied a part only of 
a house, but apparently with this difference, that they did not pay rent, 
rates, and taxes,—in fact, lived at free quarters. It is with these two 
Jatter that he had to deal, and which might be designated as “ fixed” 
and “free” companions ; the fixed being those which attached them- 
selves to another animal and there remained, and the free those 
which lived within its domicile, and could, if they willed it, leave 
their lodgings, 
Although, at first sight, apparently among the fixed companions, 
the Cione or boring sponge must be excepted, because it appeared to 
absorb the living or animal part of the shell of the oyster equally with 
_ the earthy matter, and, therefore, came within the range of the para- 
sites, 
Some “ fixed” companions were so only during their adult period 
of existence. Thus the barnacles, which attached themselves to the 
skin of whales, were, during their larval state, free swimmers, but, 
when about to take on the final Stage, they threw off their organs of 
locomotion and their eyes, and became dependent for a means of 
_ travelling on the huge whale to which they attached themselves. 
Oyster and scallop shells, especially the latter, were often covered 
with a growth of animal and vegetable life. It was no uncommon 
thing to find perfect colonies of serpule, acorn barnacles, and 
